The present disclosure relates to a wastegate valve of a turbocharger.
Japanese Laid-Open Patent Publication No. 2015-197068 discloses a turbocharger including a turbine housing and a turbine wheel accommodated in the turbine housing. The turbine housing includes a wastegate port formed to bypass the turbine wheel. A wastegate valve inside the turbine housing opens and closes the wastegate port.
The wastegate valve includes a swing arm, and the swing arm is pivotally supported by the turbine housing. The swing arm includes a shaft pivotally supported by the turbine housing and a lever extending outward from an end of the shaft in a radial direction of the shaft. The lever of the swing arm includes an insertion hole. A valve body that closes the wastegate port is attached to the lever in a manner tiltable relative to the lever. Specifically, the valve body is attached to the lever such that the center axis of the valve body is allowed to be tilted relative to the center axis of the insertion hole of the lever. The valve body includes a valve shaft inserted into the insertion hole of the lever and a valve plate arranged on an end of the valve shaft. A surface of the valve plate at a side opposite to the lever is configured to abut against an open end of the wastegate port located in an inner surface of the turbine housing so that the valve plate closes the wastegate port. An end of the valve shaft at a side opposite to the valve plate protrudes from the insertion hole, and a support plate is secured to the portion of the valve shaft protruding from the insertion hole.
Further, a substantially flat elastic member is arranged between the lever and the support plate. The elastic member includes a ring and a plurality of claws protruding inward from the inner circumferential edge of the ring in the radial direction of the ring and curved in the axial direction of the ring. The valve shaft of the valve body is inserted into a center hole in the ring of the elastic member. The ring of the elastic member abuts on one of the lever and the support plate and the distal ends of the claws of the elastic member abut on the other one of the lever and the support plate so that the elastic member biases the valve body in the axial direction of the valve shaft. To open or close the wastegate valve, the claws of the elastic member are elastically deformed to tilt the valve body relative to the lever such that the valve plate of the valve body extends in correspondence with a wall surface of the turbine housing.
The wastegate valve opens and closes the wastegate port while being exposed to the high-temperature exhaust gas drawn into the turbine housing. The claws of the elastic member repeatedly undergo elastic deformation in such a high-temperature environment. Thus, the claws of the elastic member are susceptible to wear that deteriorates the resiliency of the claws. If the claws of the elastic member are worn out and the curvature of the claws becomes small, the entire elastic member will be reduced in thickness and become loose in the wastegate valve. If the wastegate valve over-loosens, the wastegate valve may generate noise when the wastegate valve opens or closes or when exhaust gas strikes the wastegate valve.